title: Comparative least-squares analysis of hemoglobin oxygen equilibrium curves.
abstract: The oxygen-binding properties of hemoglobin have been studied at 600 microM protein concentration with organic phosphate, and analyzed by a series of different nonlinear least-squares analysis methods to determine whether reports of negligibly small values of the third overall Adair parameter, A3, are consequences of the data or a product of the data analysis. Data from other laboratories were analyzed as well. The single most important factor in creating a measurement that yields a small A3 is the use of equally weighted fitting in the Adair equation, while end-weighted fitting generally yields a larger A3. Endpoint extrapolation is ruled out as a major cause of abnormal A3 values. Monte Carlo simulations of the 600 microM results suggest that, if a small A3 were present, end weighting is at least as sensitive to a small A3 as equal weighting. We conclude that equally weighted fitting of the tetrameric Adair equation is unable to resolve the upper asymptote of the oxygen-binding data, resulting in an unusually small value for A3.
authors.affiliation: Department of Biochemistry and Biophysics, University of Pennsylvania School of Medicine, Philadelphia 19104.
authors.forename: D
authors.initials: D
authors.lastname: Myers
authors.forename: K
authors.initials: K
authors.lastname: Imai
authors.forename: T
authors.initials: T
authors.lastname: Yonetani
mesh_terms: D006441:Hemoglobin A / Q000378:metabolism*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008433:Mathematics; D008962:Models, Theoretical; D010108:Oxyhemoglobins / Q000378:metabolism*; D011336:Probability
chemical_list: D010108:Oxyhemoglobins; D006441:Hemoglobin A; C029774:oxyhemoglobin A